Simplify the following expression: $q = \dfrac{1}{8n} - \dfrac{5}{2n}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $8n$ and $2n$ $\lcm(8n, 2n) = 8n$ $ q = \dfrac{1}{1} \cdot \dfrac{1}{8n} - \dfrac{4}{4} \cdot \dfrac{5}{2n} $ $q = \dfrac{1}{8n} - \dfrac{20}{8n}$ $q = \dfrac{1 -20}{8n}$ $q = \dfrac{-19}{8n}$